Ephemeral ponds (EPs) are small wetlands that typically dry annually. The vegetation of these wetlands in glaciated eastern and central North America is understudied. We asked whether EP communities were assembled primarily from species from nearby PWs, implying neutral processes, or contained unique assemblages of species. We compared permanent wetland (PW) vegetation (n = 24) to that of EPs (n = 33) in order to describe 1) important organizing environmental gradients, 2) functional group structure and 3) diversity patterns including shared species. We speculated that EPs would have more annual species than PWs. We also hypothesized that EPs would have higher beta diversity, with a higher turnover component, than PWs. Finally, we anticipated that EP vegetation would be a subset of PW vegetation.
Results/Conclusions
Wetlands fell into three groups: EPs (n = 32), sedge meadows (SM, n =11), and lacustrine fringe wetlands (LF, n = 14). EPs had high nutrient levels, small area, and lower water temperatures compared to PWs. Both EPs and PWs were variable in water depth, pH, peat depth, and tree basal area. EPs had a higher proportion of woody indicator species (50%) compared to PWs (9.1%). Both PW types had a large proportion of graminoid cover, while EPs had higher proportions of annual, fern, and woody vegetation. Species richness guild structure was similar between the PWs but EPs had a significantly higher proportion of woody plants species. Both EPs and LFs had significantly lower site-level diversity than SMs. EPs had significantly higher beta-diversity than LFs or SMs. A large proportion of the dissimilarity was due to species turnover and not simply loss of species. The mean proportion of EP species that were also found in permanent wetlands was relatively low (~30%). EPs shared roughly the same proportion of species with SMs as they did with LFs. Our research suggests that EP plant communities do exchange species with PWs through dispersal, but that they also share unique species with each other and with the terrestrial environment.